You can do both from your theme's PostView file, exactly how depends on the theme you are using.

If you open that file you should be able to find the H1 tags.
Problem with doing a straight swap to a different heading level is that the level is also changed for single post, so maybe you want to add in some code to account for that, for example:

Thank you for this post, the h1 and h2 swap worked for me too, which was brilliant! Thanks! But, the regex code is still showing the thumbnail on the individual post page. I only want the thumbnail to show on the PostList, not the Single Post page. How
do I go about programming this?

Yes, I am wrapping the image in a conditional. I am inserting the image directly in the body of the post. Is this correct? Or should I be uploading it and using the file picker? When I insert it directly in the post and use Post.Content, The function inserts
ALL of the tags from the content not just the img tag, such as the <p> tag and <div> tags. You can see what is going on here. rag2.khambley.com. I'm using the bootstrap 3 media object to construct the post excerpt.

You know what, never mind, I got it to work brilliantly! Thank you soooo much! I'm such a bonehead, I forgot to click Only Show Description of Posts, Duh! I can't tell you what this means to me. Thanks again!